As an electrophotographic photosensitive member to be rotatably driven in an electrophotographic apparatus, a cylindrical electrophotographic photosensitive member is typically used. Electrical and mechanical external forces such as charging and cleaning are applied to the surface (circumferential surface) of an electrophotographic photosensitive member. Thus, durability to these external forces (such as resistance to wear) is demanded for the electrophotographic photosensitive member.
To meet the demand, techniques for improvement are used in the related art, for example, use of a resin having high resistance to wear (such as curable resins) in the surface layer of the electrophotographic photosensitive member.
On the other hand, examples of problems caused by increasing the resistance to wear of the circumferential surface of the electrophotographic photosensitive member include image deletion and a reduction in cleaning performance.
It is thought that the image deletion is caused by deterioration of a material used for the surface layer of the electrophotographic photosensitive member by ozone and nitrogen oxides produced by charging the circumferential surface of the electrophotographic photosensitive member, or reduction in resistance of the circumferential surface of the electrophotographic photosensitive member due to the adsorption of moisture. As the resistance to wear of the circumferential surface of the electrophotographic photosensitive member is higher, it is more difficult to refresh the circumferential surface of the electrophotographic photosensitive member (remove substances that cause the image deletion such as the deteriorated material and the adsorbed moisture), and the image deletion is more likely to be produced.
As a technique for improving the image deletion, PTL 1 discloses a technique for enhancing dot reproductivity, even if the electrophotographic photosensitive member is left to stand under a high temperature and highly humid environment, by disposing concave portions each having a depth of 0.5 μm or more and 5 μm or less and an opening longest diameter of 20 μm or more and 80 μm or less on the surface (circumferential surface) of an electrophotographic photosensitive member such that an area of the concave portions is 10000 μm2 or more and 90000 μm2 or less in a square region having a side of 500 μm, and disposing a flat part contained in a portion other than the concave portions such that an area of the flat part is 80000 μm2 or more and 240000 μm2 or less.